Adjustable clips for grazing-incidence collectors

ABSTRACT

An adjustable clip for securing a grazing-incident collector (GIC) shell to a spider having spokes is disclosed. The clip includes a base adapted to be secured to a spider spoke and having an upper surface. The clip includes a fork member having two prongs each with end pads at respective prong ends, and having a first hinge portion at an end opposite the prong ends. A hinge leaf is secured to the base upper surface and has a second hinge portion that operably engages the first hinge portion, thereby forming a hinge that allows for rotatable adjustment of the fork member relative to the base. Movement of the GIC shell when performing optical alignment is accommodated by the clip self-adjusting by its end pads moving over the GIC shell outer surface. When GIC shell alignment is achieved, the end pads are secured to the GIC shell outer surface, thereby turning the clip into a rigid support member that secures the GIC shell in place relative to the spider.

FIELD OF THE INVENTION

The present invention relates generally to grazing-incidence collectors(GICs), and in particular to adjustable clips used to secure a GIC shellto a spider.

BACKGROUND ART

EUV lithography is anticipated to be the lithographic process of choicefor producing future generations of semiconductor devices havinglinewidths on the order of 32 nm and smaller. The wavelength of the EUVradiation is nominally 13.5 nm, which calls for the use of specializedoptics to collect and image the EUV radiation.

One type of EUV optical system used to collect the radiation from thelight source is a grazing-incidence collector (GIC). A GIC typicallycomprises one or more concentrically arranged GIC shell mirrors (“GICshells”). The GIC shells are configured to receive light from the EUVsource at grazing incidence and reflect the light to form a focusedillumination beam that first forms an intermediate focus and thencreates an illumination region in the far field that is preferablyuniform to within a specification set by the overall system opticaldesign.

GICs typically require a “spider” that maintains the GIC shells in asecured position relative to one another. In some GICs, the GIC shellsare secured to the spider using clips that engage the edge or outersurface of the shell and one of the spider spokes. To date, such clipshave minimal or no adjustability, which makes optically aligning oradjusting the GIC shells problematic.

SUMMARY OF THE INVENTION

An aspect of the invention is an adjustable clip for securing agrazing-incident collector (GIC) shell to a spider having spokes. Theadjustable clip includes a base having an upper surface, wherein thebase is adapted to be secured to a spider spoke. The clip includes afork member having two prongs each with end pads at respective prongends. The fork member has, at an opposite end of the prong ends, a firsthinge portion. A hinge leaf is secured to the base upper surface and hasa second hinge portion that operably engages the first hinge portion toform a hinge that allows for rotatable adjustment of the fork memberrelative to the base. Alternatively, the base includes the second hingeportion formed integrally therewith. Movement of the GIC shell whenperforming optical alignment is accommodated by the rotation of the forkmember, which allows the end pads to slide over the GIC shell outersurface. When GIC shell alignment is achieved, the end pads are laserwelded to GIC shell outer surface, which fixes the clip in a rigidconfiguration that holds the GIC shell in place relative to the spider.

Another aspect of the invention is a method of aligning and securing aGIC shell having an outer surface and an edge to a spider having spokeseach with an upper edge. The method includes arranging the GIC shell onthe spider, with the GIC shell edge resting on portions of the upperedges of the spokes. The method also includes securing a base portion ofan adjustable clip to one of the spoke upper edges. The method furtherincludes securing a fork member to the base so that the fork member canrotate relative thereto, with the fork member having end pads that restagainst the GIC outer shell. The method then includes optically aligningthe GIC shell relative to the spider, which includes, for example,moving the GIC shell so that the fork member rotates and the end padsmove relative to the GIC shell outer surface. The method then includessecuring the end pads (e.g., via laser welding) to the GIC shell outersurface so that the adjustable clip becomes a rigid support member.Typically, a number of adjustable clips, such as three or more, are usedto secure each GIC shell to the spider.

Additional features and advantages of the invention will be set forth inthe detailed description which follows, and in part will be readilyapparent to those skilled in the art from that description or recognizedby practicing the invention as described herein, including the detaileddescription which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description present embodiments of the invention,and are intended to provide an overview or framework for understandingthe nature and character of the invention as it is claimed. Theaccompanying drawings are included to provide a further understanding ofthe invention, and are incorporated into and constitute a part of thisspecification. The drawings illustrate various embodiments of theinvention and together with the description serve to explain theprinciples and operations of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective exploded view of an example adjustable clip,also showing the set screw used to secure the clip to a spider spoke;

FIG. 2 is a perspective view of the assembled adjustable clip of FIG. 1;

FIG. 3 is a perspective view of the fork member and hinge leaf;

FIG. 4 is a perspective view of an example spider used to form a GICmirror having one or more GIC shells;

FIG. 5A and FIG. 5B are close-up perspective views of an exampleadjustable clip as secured to one of the spokes of the spider andsupporting the outer surface of a GIC shell, wherein FIG. 5A illustrateslaser welding of the hinge leaf to the base and FIG. 5B shows laserwelding of the fork member end pads to the GIC shell outer surface;

FIG. 6A is a perspective view of an example embodiment of a GIC mirrorhaving nine GIC shells shown in the process of being assembled using thespider of FIG. 4, and showing several of the adjustable clips positionedto support the outermost shell shown;

FIG. 6B is a perspective view of the GIC mirror of FIG. 2A, but with allnine GIC shells in position;

FIG. 7 is a flow diagram of an example method for aligning and securingone or more GIC shells to a spider in forming a GIC mirror; and

FIG. 8 is a perspective view similar to FIGS. 5A and 5B and illustratingan example adjustable clip that includes an actuator mechanism havingtwo adjustable screws that contact the respective end pads.

The various elements depicted in the drawing are merely representationaland are not necessarily drawn to scale. Certain sections thereof may beexaggerated, while others may be minimized. For ease of illustration,not all like elements are necessarily labeled. The drawing is intendedto illustrate an example embodiment of the invention that can beunderstood and appropriately carried out by those of ordinary skill inthe art.

DETAILED DESCRIPTION

FIG. 1 is a perspective exploded view of an example adjustable clip(“clip”) 10 according to the present invention, also showing a set screw120. FIG. 2 is a perspective view of the assembled clip 10 of FIG. 1.Clip 10 includes a fork member 20 with two prongs 30 each having an end24 with an end pad 36. In an example embodiment, fork member 20 and endpads 36 are rigid or substantially so. Example materials for clip 10include stainless steel, Inconel, Aluminum, Nickel or Nickel alloy forthermal compatibility with electroformed GIC shells.

Fork member 20 also has an opposite end 26 that includes a first hingeportion 38 that by way of example comprises a hinge knuckle 40. Hingeknuckle 40 has a hole 42 sized to accommodate a pin 50.

With reference also to FIG. 3, an example of clip 10 includes a hingeleaf 60 with a second hinge portion 61 at an edge 62. Edge 62 includesan indent 64 that defines outside hinge knuckles 70 having respectiveholes 72 formed therein sized accommodate pin 50. Indent 64 is sized toaccommodate hinge knuckle 40 so that hinge leaf 60, knuckle 40 and pin50 (or more generally, the first and second hinge portions 38 and 61,and pin 50 passing therethrough) form a hinge 80 that allows for forkmember 20 to rotate, thereby allowing for rotatable adjustability of thefork member. Hinge leaf 60 also includes a central access hole 86 foraccessing a screwing feature of a set screw, as described below.

Clip 10 further includes a base 100 having an upper surface 102 andopposite sides 104 and 106. A set screw 120 with a head 122 having ascrewing feature (shown as an Allen-type feature) is shown adjacent base100. Set screw 120 also includes a shaft 124 with a threaded end 126.Base 100 includes a slot 110 having a cross-sectional shape thataccommodates screw head 122 and a portion of shaft 124 (i.e., the headshank) adjacent thereto. Base upper surface 102 includes a central hole130 in that reaches slot 110. In an example embodiment, base uppersurface also includes a ledge 103 that accommodates knuckles 70.

Hinge leaf 60 is secured to base 100 so that holes 86 and 130 arealigned so that when set screw 120 is slid into slot 110, screwingfeature 124 can be accessed through the leaf and the base from above.

In another example embodiment, second hinge portion 61 is formedintegrally with base 100, thereby obviating the need for a separatehinge leaf 60 to be secured to base upper surface 102.

In some instances, clips 10 with two prongs 30 cannot be used in certainlocations due to mechanical interference with other elements. To avoidmechanical interference, in some locations, clips with one prong 30 maybe employed. A single-prong clip 10 is not as stiff in thecircumferential direction as the two-prong clip and is not recommendedfor sustaining lateral loads. However, this embodiment is acceptablewhen is used in appropriate combination with two-prong clips 10 wherethe latter absorb lateral loads.

Spider and Clips

FIG. 4 is a perspective view of an example spider 200 such as describedin U.S. patent application Ser. No. 12/657,650, entitled “Cooled spiderand method for grazing incidence collector,” which Application isincorporated by reference herein. A main function of spider 200 is toprovide precise, sturdy mounting and mechanical rigidity to the assemblyof one or more GIC shells 300 (which are introduced and discussed below)that form a GIC mirror. An example material for forming spider 200 isstainless steel. Other materials include Inconel, Aluminum, Nickel orNickel alloy for thermal compatibility with electroformed GIC shells300.

Spider 200 includes an outer ring 210, an inner ring 220, and aplurality of spokes 230 (six are shown by way of illustration) thatmechanically connect the inner and outer rings to provide structuralsupport to the spider. In an example where spider 200 is a cooledspider, outer ring 210, inner ring 220, and plurality of spokes 230 arefluidly connected by cooling channels 240 that are fluidly connected toinput and output cooling fluid manifolds 250A and 250B, thereby forminga cooling fluid flow path through the spider.

Spokes 230 each include an edge 234 configured support two or more GICshells 200 in a spaced apart configuration. In an example embodiment,edge 234 includes a number of steps 236 that are used to support clips10 as well as GIC shells 200 at GIC shell edge 304, as show in FIGS. 5Aand 5B.

FIG. 5A and FIG. 5B are close up views of clip 10 as arranged in anoperable configuration relative to spider 200 and a GIC shell 300, whichhas an outer surface 302 and an edge 304. Cooling lines 310 are alsoshown arranged adjacent outer surface 302. Set screw 120 is slid intoslot 110 and used to mount base 100 to a step 36. Shown on one of steps236 is an example mounting track 250 onto which base 100 can be mountedand movably adjusted along the mounting track prior to being locked inplace with set screw 120 or other securing means. In an exampleembodiment, base 100 has a lower surface 101 configured to slide alongmounting track 250.

When base 100 is secured to step 236, fork 20 is adjusted so that endpads 36 rest against GIC shell outer surface 302. However, fork member20 rotates around hinge 80 so that the position of GIC shell 300relative to spider 10 can be moved, e.g., for optical alignment of theGIC shell, while end pads 36 continue to rest against GIC shell outersurface 302. In particular, when adjusting the position of GIC shell 200relative to spider 200, end pads 36 move relative to (e.g., slide over)GIC shell outer surface 302.

When GIC shell 300 is optically aligned, then as shown in FIG. 5A, inone embodiment hinge leaf 60 is secured (e.g., laser welded) to uppersurface 102 of base 100 using a laser beam 350. This step is obviatedwhen hinge portion 61 is already formed integrally with base 100.

Also, as shown in FIG. 5B, fork member 20 is secured to GIC shell outersurface 302, e.g., by laser welding end pads 36 to the GIC outer surfacewith laser beam 350. Securing end pads 36 to GIC shell outer surfacestiffens clip 10 (i.e., fork member is no longer able to rotate) so thatthe clip serves as a rigid support that secures GIC shell 300 to spider200 in an aligned configuration. Typically, multiple adjustable clips 10are used to align and secure GIC shell 300 to spider 200.

Spider with GIC Shells

FIG. 6A is a perspective view of spider 100 supporting two GIC shells300 in the process forming a GIC mirror 400 having nine GIC shells, asshown in FIG. 6B. GIC mirror 500 has an optical axis A1. An example GICshell 300 includes the aforementioned cooling lines 310 arranged onouter surface 302, as described in U.S. patent application Ser. No.12/592,735, which application is incorporated by reference herein.

An EUV light source LS is also shown as arranged along GIC mirror axisA1 and relative to GIC mirror 400. Spider 300 is configured to operablysupport one or more GIC shells 300 in a spaced-apart and concentricconfiguration while not substantially blocking EUV radiation from beingrelayed from EUV light source LS to a GIC mirror intermediate focus.

In forming the GIC mirror 400, the innermost GIC shell 300 is arrangedon spider 100 with the GIC shell edge 304 placed on the correspondinginner steps 236 of spokes 230. Steps 236 support GIC shell 300 atrespective portions of the GIC shell edge 304. Other GIC shells 300 arethen added from the inside direction to the outside direction until thecompleted GIC mirror 400 is formed, as shown in FIG. 6B.

Example GIC Shell Alignment and Securing Method

FIG. 7 is a flow diagram of an example method for aligning and securingone or more GIC shells 300 to spider 200 in forming a GIC mirror 500.

In 701, the base 100 of a clip 10 is secured (e.g., screwed) onto spider200 at one of the innermost steps 236 of spokes 230. In an example, thisis done for at least three clips 10.

In 702, GIC shell 300 is positioned (e.g., aligned) relative to spider200, and during this positioning, clips 10 “self-adjust” by fork members20 rotating relative to their respective bases 100 at their respectivehinges 80. Once GIC shell 300 is in an optically aligned position onspider 200, then in 703, hinge leafs 60 are laser welded to theirrespective bases 100. Then in 704, end pads 36 are laser welded to GICshell outer surface 302, whereby clips 10 become rigid support members.

In the aforementioned embodiment where second hinge portion 61 is formedintegrally with base 100, step 702 is eliminated.

In 705, the next outermost GIC shell 300 is arranged on spider 200 onthe next outermost spoke steps 236, and process 700 is repeated in thedirection from the innermost GIC shell to the outermost GIC shell untilGIC mirror 400 is formed, such as shown in FIG. 6A and FIG. 6B.

Clip with Actuator Mechanism

In an additional aspect of the present invention, the use of one or moreclips 10 allow for optimization of the optical performance of GIC mirror400, not only by self-adjustment of the clips as described above, butalso through controlled manipulation of at least of one the shape (viastressing and deformation), the orientation, and the position (viatranslation and rotation) of the GIC shell 300. Such controlledmanipulation is beneficial as it allows to correct for astigmatism(i.e., deviations of perfect cylindrical symmetry), or to correctorientation and placement errors of the GIC shell.

FIG. 8 shows an example adjustable clip 10 incorporating an actuationmechanism 500 that allows for the clip to exert a controlled amount ofpressure against outer surface 302 GIC shell 300 via end pads 36. Anexample actuation mechanism 505 includes a support member 502 attachedto or formed integral with base 100. Support member 502 is configured tosupport at least one and preferably two adjustable screws 510 havingends 512 that engage pads 36, and opposite ends 516 that are configuredto be turned, e.g., by a screw-driver, allen wrench, etc. In oneexample, nuts 520 are used to secure screws 510 to support member 502 ina manner that allows for the screws to rotate.

By adjusting the positions of screws 510 relative to support member 502,a small but controllable amount of pressure is exerted against GIC shell300 through end pads 36, leading to at least one of a smalldisplacement, a small deformation, or a small change in orientation ofthe GIC shell. This makes clips 10 adjustable, and therefore makes GICshells 300 adjustable. In this embodiment, screws 510 serve as manuallyadjustable actuators.

Besides using screws 510 as adjustable actuators, other actuators can beused, such piezo electric, electromagnetic, etc. However, given that aGIC mirror is intended to be operated in a very aggressive plasmaenvironment, and that adjustments are not often required, it ispreferable to have a robust and stable actuation mechanism. Exampleactuation distances are between about 50 microns and 500 microns. Suchadjustments, along with the preferred robustness, can satisfactorily bedone using one or more screw-based actuators mechanisms as describedabove.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Thus it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An adjustable clip for securing a grazing-incident collector (GIC)shell to a spider having a spoke, comprising: a base having an uppersurface and adapted to be secured to the spoke; a fork member having twoprongs each with end pads at respective prong ends, the fork memberhaving opposite the prong ends an end with a first hinge portion; and ahinge leaf secured to the base upper surface and having a second hingeportion operably engaged with the first hinge portion to form a hingethat allows for rotatable adjustment of the fork member relative to thebase.
 2. The adjustable clip of claim 1, wherein the base is adapted tobe secured to the spoke with a set screw.
 3. The adjustable clip ofclaim 1, wherein the hinge leaf is laser welded to the based uppersurface.
 4. The adjustable clip of claim 1, further including the GICshell having an outer surface, wherein the end pads are secured to theGIC shell outer surface so that the adjustable clip provides rigidsupport between the GIC shell and the spider.
 5. The adjustable clip ofclaim 4, wherein the end pads are laser welded to the GIC shell outersurface.
 6. The adjustable clip claim 1, further including a pin passingthrough the first and second hinge portions to maintain the first andsecond hinge portions in rotational engagement.
 7. The adjustable clipof claim 1, further including an actuation mechanism configured to putpressure on the end pads.
 8. The adjustable clip of claim 7, wherein theactuation mechanism includes two manually adjustable screws havingrespective ends that press against the end pads.
 9. An adjustable clipfor securing a grazing incidence collector (GIC) having an outersurface, comprising: a fork member having end pads and a first hingeportion; and a base portion having an upper surface and a second hingeportion operably engaged with the first hinge portion so that the forkmember is rotationally adjustable relative to the base portion.
 10. Theadjustable clip of claim 9, further comprising: a leaf portion securedto the upper surface of the base portion and that includes the secondhinge portion.
 11. The adjustable clip of claim 10, wherein the leafportion is laser welded to the surface of the base portion.
 12. Theadjustable clip of claim 9, wherein the base portion is adapted to besecured to a spoke of a spider using a set screw.
 13. The adjustableclip of claim 9, further including the GIC shell, wherein the end padsare laser welded to the outer surface of the GIC shell and the baseportion is secured to a spider to form a rigid support between the GICshell and the spider.
 14. The adjustable clip of claim 9, furtherincluding an actuation mechanism configured to put pressure on the endpads.
 15. The adjustable clip of claim 14, wherein the actuationmechanism includes two manually adjustable screws having respective endsthat press against the end pads.
 16. A method of aligning and securing agrazing incidence collector (GIC) shell having an outer surface and anedge to a spider having spokes each with an upper edge, comprising:arranging the GIC shell on the spider, with the edge resting on portionsof the upper edges of the spokes; securing a base portion of anadjustable clip to the upper edge of the spokes; securing a fork memberto the base portion so that the fork member can rotate relative thereto,the fork member having end pads that rest against the outer GIC shell;optically aligning the GIC shell relative to the spider while the forkmember self-adjusts by rotating relative to the base portion; andsecuring the end pads to the outer surface of the GIC shell to form arigid support between the GIC shell and the spider.
 17. The method ofclaim 16, further comprising securing the fork member to the baseportion using a hinge.
 18. The method of claim 17, wherein the baseportion includes an upper surface and including forming the hinge usinga hinge leaf that is secured to the upper surface of the base portionand that operably engages a hinge knuckle of the fork member.
 19. Themethod of claim 18, further comprising laser welding the hinge leaf tothe upper surface of the base portion.
 20. The method of claim 17,further comprising laser welding the end pads to the outer surface ofthe GIC shell.
 21. The method of claim 17, including carrying out thesteps therein for at least three adjustable clips per each GIC shell.22. The method of claim 21, including carrying out the steps therein fortwo or more GIC shells.
 23. The method of claim 16, further comprisingapplying pressure to the end pads to adjust at least one of a position,shape and an orientation of the GIC shell.
 24. A GIC mirror, comprising:a) one or more GIC shells each having an outer surface; b) a spiderhaving spokes that support the one or more GIC shells; c) for each GICshell, at least one adjustable clip secured to the spokes and to theouter surface of the GIC shell, the at least one adjustable clip having:i) a base portion having an upper surface; and ii) a fork member havingprongs with end pads, the fork member being secured to the base portionat a hinge that allows the fork member to rotate relative to the baseportion prior to securing the end pads to the outer surface of the GICshell, and wherein the end pads are secured to the outer surface of theGIC shell.
 25. The GIC mirror of claim 24, further comprising first andsecond adjustable screws that pass through a support member secured toor formed integrally with the base portion, the first and secondadjustable screws having ends that contact the respective end pads so asto apply pressure thereto.